Yes, at least one. I have a monocular magnifying viewfinder for the Cambo. Comes in handy sometimes.
If you don't want to troll eBay, you can always try Calumet. As they now own Cambo, they always have stock of the accessories. I have even seen this viewer in their used listings.
I have had both the cambo monocular and the binocular reflex viewer. The binocular viewer is incredible and its liek seeing all over again. Imagine a RB viewfinder x4 with stereo vision. Very nice but its big.
I opted for the monocular for hiking. Its small light and still better than a dark cloth but not up to the binocular viewfinder.
Here is is set up on my Super Graphic. Down the page.
There is also a revolving monocular viewer. Try Jim at Midwest Photo Exchange. I sold him one of the revolving finders a while back. That one may be gone, but he does carry used items like this.